Twin scroll turbocharger with EGR takeoffs

ABSTRACT

Systems and methods for operating a twin scroll turbocharged engine with a junction configured to selectively control exhaust gas delivery to an exhaust gas recirculation system and a twin scroll turbine are provided.

FIELD

The present application relates to twin scroll turbochargers and exhaustgas recirculation.

BACKGROUND AND SUMMARY

Twin scroll turbocharger configurations may be used in turbochargedengines. A twin scroll turbocharger configuration may separate an inletto a turbine into two separate passages connected to exhaust manifoldrunners so that exhaust from engine cylinders whose exhaust gas pulsesmay interfere with each other are separated.

For example, on an I4 engine with a cylinder firing order of 1-3-4-2,exhaust manifold runners 1 and 4 may be connected to a first inlet of atwin scroll turbine and exhaust manifold runners 2 and 3 may beconnected to a second inlet of said twin scroll turbine, where thesecond inlet is different from the first inlet. Separating exhaust gaspulses in this way may, in some examples, result in an increase inefficiency of exhaust gas delivery to a turbine.

However, the inventors herein have recognized that under some engineoperating conditions separating exhaust gas pulses as described abovemay reduce an efficiency of exhaust gas delivery to a turbine. Forexample, the inventors herein have recognized that under certain engineoperating conditions, e.g., high speed and high load conditions,separating exhaust gas pulses as described above may result in anincrease in backpressure and pumping work due to, for example, anincrease in exhaust gas enthalpy.

The inventors herein have also recognized that high pressure exhaust gasrecirculation (EGR) may be used during some conditions in engines with atwin scroll turbocharger configuration. The inventors herein haverecognized that if exhaust gas is taken off the exhaust feeding atwin-scroll turbine, pressure pulsations of the exhaust gas driving theturbine may be disadvantageously dampened.

In one example approach, a method for operating an engine with a twinscroll turbine and an EGR system comprises: during a first condition,fluidically separating the scrolls of the twin scroll turbine andoperating said engine with reduced EGR; and during a second condition,fluidically combining the scrolls of the twin scroll turbine andoperating said engine with increased EGR.

In this way, an engine including a twin scroll turbochargerconfiguration may be operated using the twin scroll feature in a firstmode, and effectively operated using a single scroll to drive theturbine in a second mode, depending on various engine operatingconditions.

Additionally, when high pressure EGR is used in an engine with a twinscroll configuration, the exhaust gas supplying the EGR system may betaken off both sides of the twin scroll inlet to the turbine. In thisway, dampening and/or unevenness of pressure pulsations of exhaust gasdriving the turbine may be reduced.

For example, by opening up the high pressure EGR system andcommunication between scrolls of a twin scroll turbine during certainengine operating conditions, e.g., during high speed/high loadconditions, the high pressure EGR may be used for enrichment reductionand the turbine inlet communication may reduce back pressure andincrease a horsepower capability of the engine.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of an engine including a twin scrollturbocharger and an exhaust gas recirculation (EGR) system.

FIG. 2 shows an example high pressure EGR take-off and twin scrollcommunication valve coupled to an engine.

FIGS. 3-5 show various viewpoints of an example high pressure EGRtake-off and twin scroll communication valve.

FIG. 6 shows an example method for operating a twin scroll turbochargedengine with a junction configured to selectively control exhaust gasdelivery to an exhaust gas recirculation system and a twin scrollturbine.

FIG. 7 shows an example method for operating a twin scroll turbochargedengine without EGR.

DETAILED DESCRIPTION

The following description relates to systems and methods for operatingan engine including a twin scroll turbocharger system and an exhaust gasrecirculation (EGR) system, for example as shown in FIG. 1.

Twin scroll turbocharger configurations may be used in turbochargedengines. For example, twin scroll turbocharger configurations may beused in gasoline engines where variable vane turbocharger technology maybe prohibited due to high operating temperatures of the engine.

In contrast to a single scroll turbocharger configuration which includesa single exhaust gas inlet to the turbine, a twin scroll turbochargerconfiguration may separate an inlet to a turbine into two separatepassages connected to exhaust manifold runners so that exhaust fromcylinders whose exhaust gas pulses may interfere with each other areseparated.

For example, on an I4 engine with a cylinder firing order of 1-3-4-2,exhaust manifold runners 1 and 4 may be connected to a first inlet of atwin scroll turbine and exhaust manifold runners 2 and 3 may beconnected to a second inlet of said twin scroll turbine, where thesecond inlet is different from the first inlet.

Separating exhaust gas pulses in this way may, in some examples, resultin an increase in boost response and turbo efficiency. Advantages ofusing a twin scroll turbocharger configuration may further includereduction in turbo lag and an increase in volumetric efficiency of theengine. During certain conditions, a greater amount of positive valveoverlap and a higher ignition delay may be used in an engine including atwin scroll turbocharger. Additionally, lower exhaust gas temperaturesmay be obtained and leaner air/fuel ratios may be employed.

However, during certain engine operating conditions, separating exhaustgas pulses as described above may reduce an efficiency of exhaust gasdelivery to a turbine. For example, under certain engine operatingconditions, e.g., high speed and high load conditions, separatingexhaust gas pulses as described above may result in an increase inbackpressure and pumping work due to, for example, an increase inexhaust gas enthalpy.

Additionally, high pressure exhaust gas recirculation (EGR) may be usedduring some conditions in engines with twin scroll turbochargers.However, in some examples, if exhaust gas is taken off the exhaustfeeding a twin-scroll turbine, pressure pulsations of the exhaust gasdriving the turbine may be disadvantageously dampened.

In order to at least partially address these issues, a junctionconfigured to selectively control exhaust gas delivery to an EGR systemand a twin scroll turbine is provided, e.g., as shown in FIGS. 1-5.

As shown in the example method in FIG. 6, in a first mode such ajunction may be configured to supply exhaust gas to an EGR system fromboth scrolls of a twin scroll turbine while putting the twin scrolls influid communication. In a second mode, such a junction may be configuredto shut-off exhaust flow to an EGR system and fluidically separate thescrolls of a twin scroll turbine.

In this way, an engine including a twin scroll turbochargerconfiguration may be operated using the twin scroll feature in a firstmode, and effectively operated using a single scroll to drive theturbine in a second mode, depending on various engine operatingconditions.

Additionally, when high pressure EGR is used in an engine with a twinscroll configuration, the exhaust gas supplying the EGR system may betaken off both sides of the twin scroll inlet to the turbine. In thisway, dampening and/or unevenness of pressure pulsations of exhaust gasdriving the turbine may be reduced.

For example, by opening up the high pressure EGR system andcommunication between the twin scroll turbine inlets during certainengine operating conditions, e.g., during high speed/high loadconditions, the high pressure EGR may be used for enrichment reductionand the turbine inlet communication may reduce back pressure andincrease a horsepower capability or power of the engine.

Turning now to FIG. 1, a schematic diagram of an engine 10, which may beincluded in a propulsion system of an automobile, is shown. Engine 10may be controlled at least partially by a control system includingcontroller 12 and by input from a vehicle operator 14 via an inputdevice 16. In this example, input device 16 includes an acceleratorpedal and a pedal position sensor 18 for generating a proportional pedalposition signal PP.

Engine 10 may include a plurality of combustion chambers (i.e.,cylinders). In the example shown in FIG. 1, Engine 10 includescombustion chambers 20, 22, 24, and 26, arranged in an inline 4configuration. It should be understood, however, that though FIG. 1shows four cylinders, engine 10 may include any number of cylinders inany configuration, e.g., V-6, I-6, V-12, opposed 4, etc.

Though not shown in FIG. 1, each combustion chamber (i.e., cylinder) ofengine 10 may include combustion chamber walls with a piston positionedtherein. The pistons may be coupled to a crankshaft so thatreciprocating motions of the pistons are translated into rotationalmotion of the crankshaft. The crankshaft may be coupled to at least onedrive wheel of a vehicle via an intermediate transmission system, forexample. Further, a starter motor may be coupled to the crankshaft via aflywheel to enable a starting operation of engine 10.

Each combustion chamber may receive intake air from an intake manifold28 via an air intake passage 30. Intake manifold 28 may be coupled tothe combustion chambers via intake ports. For example, intake manifold28 is shown in FIG. 1 coupled to cylinders 20, 22, 24, and 26 via intakeports 32, 34, 36, and 38 respectively. Each respective intake port maysupply air and/or fuel to the respective cylinder for combustion.

Each combustion chamber may exhaust combustion gases via an exhaust portcoupled thereto. For example, exhaust ports 40, 42, 44 and 46, are shownin FIG. 1 coupled to cylinders 20, 22, 24, 26, respectively. Eachrespective exhaust port may direct exhaust combustion gases from arespective cylinder to an exhaust manifold or exhaust passage.

Each cylinder intake port can selectively communicate with the cylindervia an intake valve. For example, cylinders 20, 22, 24, and 26 are shownin FIG. 1 with intake valves 48, 50, 52, and 54, respectively. Likewise,each cylinder exhaust port can selectively communicate with the cylindervia an exhaust valve. For example, cylinders 20, 22, 24, and 26 areshown in FIG. 1 with exhaust valves 56, 58, 60, and 62, respectively. Insome examples, each combustion chamber may include two or more intakevalves and/or two or more exhaust valves.

Though not shown in FIG. 1, in some examples, each intake and exhaustvalve may be operated by an intake cam and an exhaust cam.Alternatively, one or more of the intake and exhaust valves may beoperated by an electromechanically controlled valve coil and armatureassembly. The position of an intake cam may be determined by an intakecam sensor. The position of exhaust cam may be determined by an exhaustcam sensor.

Intake passage 30 may include a throttle 64 having a throttle plate 66.In this particular example, the position of throttle plate 66 may bevaried by controller 12 via a signal provided to an electric motor oractuator included with throttle 64, a configuration that is commonlyreferred to as electronic throttle control (ETC). In this manner,throttle 64 may be operated to vary the intake air provided thecombustion chambers. The position of throttle plate 66 may be providedto controller 12 by throttle position signal TP from a throttle positionsensor 68. Intake passage 30 may include a mass air flow sensor 70 and amanifold air pressure sensor 72 for providing respective signals MAF andMAP to controller 12.

In FIG. 1, fuel injectors are shown coupled directly to the combustionchambers for injecting fuel directly therein in proportion to a pulsewidth of a signal FPW received from controller 12 via an electronicdriver, for example. For example, fuel injectors 74, 76, 78, and 80 areshown in FIG. 1 coupled to cylinders 20, 22, 24, and 26, respectively.In this manner, the fuel injectors provide what is known as directinjection of fuel into the combustion chamber. Each respective fuelinjector may be mounted in the side of the respective combustion chamberor in the top of the respective combustion chamber, for example. In someexamples, one or more fuel injectors may be arranged in intake passage28 in a configuration that provides what is known as port injection offuel into the intake ports upstream of combustion chambers. Though notshown in FIG. 1, fuel may be delivered to the fuel injectors by a fuelsystem including a fuel tank, a fuel pump, a fuel line, and a fuel rail.

The combustion chambers of engine 10 may be operated in a compressionignition mode, with or without an ignition spark. In some examples, adistributorless ignition system (not shown) may provide an ignitionsparks to spark plugs coupled to the combustion chambers in response tocontroller 12. For example, spark plugs 82, 84, 86, and 88 are shown inFIG. 1 coupled to cylinders 20, 22, 24, and 26, respectively.

Engine 10 may include a turbocharger 90. Turbocharger 90 may be includea turbine 92 and a compressor 94 coupled on a common shaft 96. Theblades of turbine 92 may be caused to rotate about the common shaft as aportion of the exhaust gas stream discharged from engine 10 impingesupon the blades of the turbine. Compressor 94 may be coupled to turbine92 such that compressor 94 may be actuated when the blades of turbine 92are caused to rotate. When actuated, compressor 94 may then directpressurized fresh gas to air intake manifold 28 where it may then bedirected to engine 10.

Engine 10 may employ a dual scroll (or twin scroll or two-pulse)turbocharger system 98 wherein at least two separate exhaust gas entrypaths flow into and through turbine 92. A dual scroll turbochargersystem may be configured to separate exhaust gas from cylinders whoseexhaust gas pulses interfere with each other when supplied to turbine92. For example, FIG. 1 shows a first scroll 100 and a second scroll 102which are used to supply separate exhaust streams to turbine 92.

For example, if a four-cylinder engine (e.g., an I4 engine such as shownin FIG. 1) has a firing sequence of 1-3-4-2 (e.g., cylinder 20 followedby cylinder 24 followed by cylinder 26 followed by cylinder 22), thencylinder 20 may be ending its expansion stroke and opening its exhaustvalves while cylinder 22 still has its exhaust valves open. In asingle-scroll or undivided exhaust manifold, the exhaust gas pressurepulse from cylinder 20 may interfere with the ability of cylinder 22 toexpel its exhaust gases. However, by using a dual scroll system whereinexhaust ports 40 and 46 from cylinders 20 and 26 are connected to oneinlet of the first scroll 100 and exhaust ports 42 and 44 from cylinders22 and 24 are connected to the second scroll 102, exhaust pulses may beseparated and pulse energy driving the turbine may be increased.

Turbine 92 may include at least one wastegate to control an amount ofboost provided by said turbine. In a dual scroll system, each scroll mayinclude a corresponding wastegate to control the amount of exhaust gaswhich passes through turbine 92. For example, in FIG. 1, the firstscroll 100 includes a first wastegate 104. First wastegate 104 includesa wastegate valve 106 configured to control an amount of exhaust gasbypassing turbine 92. Likewise, the second scroll 102 includes a secondwastegate 108. Second wastegate 108 includes a wastegate valve 110configured to control an amount of exhaust gas bypassing turbine 92.

Exhaust gases exiting turbine 92 and/or the wastegates may pass throughan emission control device 112. Emission control device 112 can includemultiple catalyst bricks, in one example. In another example, multipleemission control devices, each with multiple bricks, can be used. Insome examples, emission control device 112 may be a three-way typecatalyst. In other examples, emission control device 112 may include oneor a plurality of a diesel oxidation catalyst (DOC), selective catalyticreduction catalyst (SCR), and a diesel particulate filter (DPF). Afterpassing through emission control device 112, exhaust gas may be directedto a tailpipe 114.

Engine 10 may include an exhaust gas recirculation (EGR) system 116. EGRsystem 116 may deliver a portion of exhaust gas exiting engine 10 intothe engine air intake passage 30. The EGR system includes an EGR conduit118 coupled to the scrolls 100 and 102 and coupled to the air intakepassage 30. In some examples, EGR conduit 118 may include an EGR valve120 configured to control an amount of recirculated exhaust gas.

Under some conditions, EGR system 116 may be used to regulate thetemperature and or dilution of the air and fuel mixture within thecombustion chambers, thus providing a method of controlling the timingof ignition during some combustion modes. Further, during someconditions, a portion of combustion gases may be retained or trapped inthe combustion chamber by controlling exhaust valve timing.

In some examples, controller 12 may be a conventional microcomputerincluding: a microprocessor unit, input/output ports, read-only memory,random access memory, keep alive memory, and a conventional data bus.Controller 12 is shown in FIG. 1 receiving various signals from sensorscoupled to engine 10, in addition to those signals previously discussed,including: engine coolant temperature (ECT) from a temperature sensor128; an engine position sensor 130, e.g., a Hall effect sensor 118sensing crankshaft position. Barometric pressure may also be sensed(sensor not shown) for processing by controller 12. In some examples,engine position sensor 130 produces a predetermined number of equallyspaced pulses every revolution of the crankshaft from which engine speed(RPM) can be determined. Additionally, various sensors may be employedto determine turbocharger boost pressure. For example, a pressure sensor132 may be disposed in intake 30 downstream of compressor 94 todetermine boost pressure. Additionally, each scroll of the dual scrollsystem 98 may include various sensors for monitoring operatingconditions of the duel scroll system. For example, the first scroll 100may include an exhaust gas sensor 134 and the second scroll 102 mayinclude an exhaust gas sensor 136. Exhaust gas sensors 134 and 136 maybe any suitable sensor for providing an indication of exhaust gasair/fuel ratio such as a linear oxygen sensor or UEGO (universal orwide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO(heated EGO), a NOx, HC, or CO sensor.

EGR conduit 118 may be coupled to both the first scroll 100 and thesecond scroll 102 of the dual scroll system 98 at a junction 122 so thatEGR may be taken off both sides of the dual scroll inlet to the turbine,e.g., to reduce uneven pressure pulsations in driving turbine 92. Forexample, a first EGR takeoff 138 may be disposed in first scroll 100 anda second EGR takeoff 140 may be disposed in second scroll 102.

Junction 122 may include a valve 124 positioned in the EGR takeoff fromfirst scroll 100 and a valve 126 positioned in the EGR takeoff fromsecond scroll 102. In some examples, valves 124 and 126 may be dualbutterfly flaps configured to open and close synchronously. Valves 124and 126 may be cooled in some examples. For example, the valves may bewater-cooled by circulating a suitable coolant, e.g. water or the like,through at least a portion of the valves. As another example, the valvesmay be air-cooled, e.g., by circulating air through at least a portionof the valves. In this way, exhaust gases may be cooled while passingover the valves.

In a first mode, junction 122 may be configured to supply exhaust gas toEGR system 116 from both scrolls while putting the first and secondscrolls in fluid communication. For example, in the first mode valves124 and 126 may be opened to allow exhaust gas to flow into EGR system116 while putting the first and second scrolls in fluid communication.

In a second mode, junction 122 may be configured to shut-off exhaustflow to EGR system 116 and fluidically separate the first and secondscrolls. For example, in the second mode, valves 124 and 126 may beclosed to shut-off exhaust flow to the EGR system while fluidicallyseparating the first and second scrolls.

In some examples, valves 124 and 126 may be adjusted to meter the amountof exhaust gas entering the EGR system and the amount of fluidcommunication between the first and second scrolls. For example, valves124 and 126 may be partially opened to reduce an amount of exhaust gasprovided to the EGR system and to reduce an amount of fluidcommunication between the first and second scrolls.

For example, valves 124 and 126 positioned in the EGR takeoffs mayfunction to shutoff the high pressure EGR volume during engine operatingconditions where that EGR volume may be detrimental to pressurepulsation driving of the turbine. For example, valves 124 and 126 may beclosed during engine accelerations or high load/low speed conditions. Inthis example, the first and second scrolls are fluidically separated,e.g., to increase driving of the turbine.

As another example, valves 124 and 126 positioned in the EGR takeoffsmay function to provide high-pressure EGR during engine operatingconditions where air/fuel dilution may be advantageous. For example,valves 124 and 126 may be opened during engine high speed and high loadconditions when high pressure EGR may be used for enrichment reduction.In this example, the first and second scrolls are put into fluidcommunication, e.g., to reduce backpressure.

Turning now to FIGS. 2-5, an example junction 122 configured toselectively control exhaust gas delivery to an EGR system and a twinscroll turbine is shown from various viewpoints. Specifically, FIG. 2shows a side view of example junction 122 coupled to engine 10, FIG. 3shows a perspective side view of junction 122, FIG. 4 shows a back viewof junction 122, and FIG. 5 shows a top view of junction 122. Theexample junction in FIGS. 2-5 is shown approximately to scale.

Junction 122 may be composed of a variety of suitable materials and maybe formed from one or more components. In some examples, junction 122may be substantially composed of one or more metal materials, e.g. steelor the like. In other examples, the junction may be substantiallycomposed of a polymer material such as a thermoplastic. In still otherexamples, junction 122 may be composed of a combination of variousmaterials, e.g., both metal and polymer materials.

In some examples, junction 122 may comprise a plurality of components,e.g., junction 122 may be formed from a plurality of components coupledtogether using suitable coupling methods, e.g., using a suitable weldingprocess and/or via suitable mechanical couplings such as bolts and thelike. In other examples, junction 122 may be formed as a single unit,e.g., via suitable molding techniques and/or machining techniques.

Junction 122 includes a plurality of passages partitioned by walls andvarious valves. In some examples, a thickness of the walls of junction122 may depend on expected temperatures of exhaust gas passing throughthe passages. Thus a thickness of the walls may be predetermined basedon the type of engine employed. For example, an engine which generateshigher exhaust temperatures (e.g., a gasoline engine) may have thickerwalls than an engine which generates lower exhaust temperatures (e.g., adiesel engine). Additionally, thickness of the junction walls may dependon a size of the engine employed, e.g., number of cylinders, compressionratio of the cylinders, etc.

Junction 122 includes a dual-bored body shown generally at 200 in FIGS.2-5. Dual-bored body 200 includes a first bore 100 and a second bore102, where the first bore 100 corresponds to the first scroll 100 andthe second bore 102 corresponds to the second scroll 102 shownschematically in FIG. 1. The first and second bores on body 200 aresubstantially hollow apertures extending through the body of junction122.

Dual-bored body 200 is part of a twin scroll turbocharger system, e.g.,as shown schematically at 98 in FIG. 1. As described above, a twinscroll turbocharger system may be configured to separate exhaust gasfrom cylinders whose exhaust gas pulses interfere with each other whensupplied to a turbine, e.g., turbine 92 shown in FIG. 1. The first bore100 of body 200 provides a communication passage between the exhaust ofa first set of cylinders and the twin scroll turbine. The second bore102 of body 200 provides a communication passage between the exhaust ofa second set of cylinders, different from the first set of cylinders,and the twin scroll turbine.

For example, if a four-cylinder engine (e.g., an I4 engine such as shownin FIG. 1) has a firing sequence of 1-3-4-2 (e.g., cylinder 20 followedby cylinder 24 followed by cylinder 26 followed by cylinder 22), thenthe first set of cylinders may include cylinders 20 and 26 and thesecond set of cylinders may include cylinders 22 and 24. In this way,under some conditions, the first and second bores may separate exhaustgas from cylinders whose exhaust gas pulses interfere with each otherwhen supplied to the turbine.

The first and second bores in dual-bored body 200 form first and secondexhaust gas passages, respectively, therethrough. The first and secondpassages in body 200 may have a variety of shapes, sizes, and contours.In some examples, the sizes, shapes, and/or contours of the bores may beconfigured to increase energy conferred to the turbine by the exhaustgases flowing therethrough. For example, the first and second bores mayhave a twisting and/or curved shape, e.g. as shown in FIGS. 3 and 4 at202, to increase energy conferred to the turbine by exhaust gases. Inthis way, an acceleration of the exhaust gas may be increased whenpassing through the bores.

Junction 122 includes an engine mount shown generally at 204 in FIGS.2-5. Engine mount 204 is coupled to dual-bored body 200 and comprises asubstantially flat mounting portion configured to couple with engine 10and fluidically couple the first bore 100 and the second bore 102 inbody 200 to the exhaust of a first set of cylinders and to the exhaustof a second set of cylinders, different from the first set of cylinders,respectively. For example, if a four-cylinder engine (e.g., an I4 enginesuch as shown in FIG. 1) has a firing sequence of 1-3-4-2 (e.g.,cylinder 20 followed by cylinder 24 followed by cylinder 26 followed bycylinder 22), then the first set of cylinders may include cylinders 20and 26 and the second set of cylinders may include cylinders 22 and 24.FIG. 2 shows junction 122 coupled to engine 10 via engine mount 204.

In some examples, engine mount 204 may comprise a flange configured toassist in a coupling of junction 122 to the engine. Thus engine mount204 may extend a distance beyond the bore apertures in the engine mountto form the flange. The engine mount may include various featuresconfigured to assist in coupling junction 122 to the engine, e.g., via amechanical coupling.

For example, the engine mount may include a plurality of apertures 206sized to receive mechanical coupling elements, where the mechanicalcoupling elements may assist in coupling junction 122 to the engine. Forexample, mechanical coupling elements may include bolts or the like. Insome examples, engine mount 204 may be welded to the engine instead ofor in addition to the mechanical couplings described above.

A plurality of features corresponding to the plurality of apertures 206may be included on engine 10 to assist in coupling junction 122 to theengine. In some examples, the plurality of features included on theengine may include apertures to receive coupling elements. For example,if bolts are used to attach junction 122 to engine 10 via apertures 206,the plurality of features included on the engine may include threadedapertures configured to receive said bolts.

Junction 122 includes a turbine mount shown generally at 208 in FIGS.2-5. Turbine mount 208 is coupled to an end of the dual-bored bodyopposing the engine mount 204. Turbine mount 208 comprises asubstantially flat mounting portion configured to couple with atwin-scroll turbine, e.g., turbine 92, and fluidically couple the firstbore 100 and the second bore 102 in body 200 to a first scroll and asecond scroll, respectively, in the twin-scroll turbine.

In some examples, turbine mount 208 may comprise a flange configured toassist in coupling of junction 122 to the turbine. Thus turbine mount208 may extend a distance beyond the bore apertures in the turbine mountto form the flange. The turbine mount may include various featuresconfigured to assist in coupling junction 122 to the turbine, e.g., viaa mechanical coupling.

For example, the turbine mount may include a plurality of apertures 210sized to receive mechanical coupling elements, where the mechanicalcoupling elements may assist in coupling junction 122 to the turbine.For example, mechanical coupling elements may include bolts or the like.In some examples, turbine mount 208 may be welded to the turbine insteadof or in addition to the mechanical couplings described above.

A plurality of features corresponding to the plurality of apertures 210may be included on the twin-scroll turbine to assist in couplingjunction 122 to the turbine. In some examples, the plurality of featuresincluded on the turbine may include apertures to receive couplingelements. For example, if bolts are used to attach junction 122 toturbine 92 via apertures 210, the plurality of features included on theturbine may include threaded apertures configured to receive said bolts.

Junction 122 includes an EGR takeoff body shown generally at 212 inFIGS. 2-5. EGR takeoff body 212 is coupled to dual-bored body 200 andincludes a first EGR takeoff 138 fluidically coupled to first bore 100in dual-bored body 200 and a second EGR takeoff 140 fluidically coupledto second bore 102 in dual-bored body 200.

The first EGR takeoff 138 and the second EGR takeoff 140 are passagesextending through the EGR takeoff body 212 and are configured tocommunicate with a common EGR conduit, e.g., EGR conduit 118 shownschematically in FIG. 1.

EGR takeoff body 212 includes a first valve 124 positioned in first EGRtakeoff 138 from first bore 100 and a second valve 126 positioned in thesecond EGR takeoff 140 from second bore 102. In some examples, the firstvalve 124 and second valve 126 may be dual butterfly flaps configured toopen and close synchronously. In such a case, the first and secondvalves may be coupled to a common rotating valve shaft 214, where thevalve shaft may be rotated by a controller, e.g., controller 12, to openand close the dual butterfly valves.

Valves 124 and 126 may be cooled in some examples. For example, thevalves may be water-cooled by circulating a suitable coolant, e.g. wateror the like, through at least a portion of the valves. As anotherexample, the valves may be air-cooled, e.g., by circulating air throughat least a portion of the valves. In this way, exhaust gases may becooled while passing over the valves.

EGR takeoff body 212 includes an EGR conduit mount shown generally at216 in FIGS. 2-5. EGR conduit mount 216 comprises a substantially flatmounting portion configured to couple with an EGR conduit, e.g., EGRconduit 118 shown in FIG. 1.

In some examples, EGR conduit mount 216 may comprise a flange configuredto assist in coupling of junction 122 to the turbine. Thus, EGR conduitmount 216 may extend a distance beyond the EGR takeoff apertures 138 and140 to form the flange. The EGR conduit mount 216 may include variousfeatures configured to assist in coupling an EGR conduit to the EGRtakeoff body 212, e.g., via a mechanical coupling.

For example, EGR conduit mount 216 may include a plurality of apertures218 sized to receive mechanical coupling elements, where the mechanicalcoupling elements may assist in coupling an EGR conduit to the EGRtakeoff body 212. For example, mechanical coupling elements may includebolts or the like. In some examples, EGR conduit mount 216 may be weldedto an EGR conduit instead of or in addition to the mechanical couplingsdescribed above.

A plurality of features corresponding the plurality of apertures 218 maybe included an EGR conduit to assist in coupling EGR conduit mount 216to the EGR conduit. In some examples, the plurality of features includedon an EGR conduit may include apertures to receive coupling elements.For example, if bolts are used to attach EGR conduit mount 216 to EGRconduit 118 via apertures 218, the plurality of features included on theEGR conduit may include threaded apertures configured to receive saidbolts.

FIG. 6 shows an example method 600 for operating a twin scrollturbocharged engine with a junction configured to selectively controlexhaust gas delivery to an EGR system and a twin scroll turbine, e.g.,junction 122 described above.

At 602, method 600 includes determining if entry conditions are met. Insome examples, determining if entry conditions are met may includedetermining if conditions for using separated twin scrolls to drive atwin scroll turbine are met.

Conditions for using separated twin scrolls to drive a twin scrollturbine may include a variety of engine operating conditions whereinseparated scrolls driving the twin scroll turbine may be advantageous toengine operation.

As described above, separating the scrolls may, during some conditions,increase boost response and turbo efficiency. For example, conditionsfor using separated twin scrolls to drive the turbine may include engineoperating conditions where the turbine spools up, e.g., engine operatingconditions where a speed of the turbine increases from a first speed toa second speed, where the second speed is greater than the first speed,e.g., during engine acceleration conditions.

Thus, entry conditions may include high load and low speed (RPM) engineoperating conditions, e.g., when a high engine torque is requested by anoperator of the engine, e.g., via an acceleration pedal. For example,the entry conditions may include an engine load greater than a firstpredetermined threshold value and engine speed less a secondpredetermined threshold value.

In some examples, determining if entry conditions are met may includedetermining if conditions for operating the engine with high pressureEGR are not met or determining if high pressure EGR is not anticipated.

For example, high pressure EGR may be used for enrichment reduction ofthe air/fuel ratio entering the engine. During high speed/high loadengine operating conditions, high pressure EGR may be employed forenrichment reduction. Thus conditions for operating the engine with highpressure EGR may not be met during low speed conditions.

Other examples of conditions for operating the engine with high pressureEGR not being met may include engine operating conditions which have lowNOX emissions, low charge density, low engine temperature, and/orcombinations thereof.

If entry conditions are met at 602, method 600 proceeds to 604. At 604,method 600 includes operating the engine with a reduced amount of EGRand with separated twin scrolls driving the twin scroll turbine. Forexample, at 604 engine exhaust gas pulses may be separated to drive theturbine and a first amount of exhaust gas may be recirculated to theengine. In some examples, at 604, the engine may be operated withoutEGR. For example, valves 124 and 126 may be closed in order to at leastpartially shut off the EGR takeoffs from the twin scrolls and separatethe twin scrolls for driving of the turbine.

At 606, method 600 includes adjusting operating parameters in responseto operating the engine without EGR and with separate twin scrolls.Examples of engine operating parameters which may be adjusted inresponse to operating the engine without EGR and with separate twinscrolls include the air/fuel ratio, throttle position, valve overlap,ignition timing, etc. For example, valve overlap may be increased and/orignition delay may be increased, e.g., spark timing may be retarded. Forexample, the engine may be operated with a first amount of positivevalve overlap in at least one cylinder of the engine and/or the enginemay be operated with a first amount of spark retard in at least onecylinder of the engine. In some examples, the engine may be operatedwith a first, increased, amount of fuel.

However, if entry conditions are not met at 602, method 600 proceeds to608. At 608, method 600 includes operating the engine with an increasedamount of EGR, e.g., relative to the amount of EGR used in step 604described above, and with both scrolls of the twin scroll turbine influid communication. In this case, the twin scroll turbine may beeffectively operated in a single scroll mode, wherein pulse separationmay be reduced. For example, at 608 engine exhaust gas pulses may becombined to drive the turbine and a second amount of exhaust gas may berecirculated to the engine, where the second amount of exhaust gas isgreater than the first amount of exhaust gas used in step 604 describedabove. For example valves 124 and 126 in the EGR takeoff body may be atleast partially opened to provide exhaust gas take from both scrolls tothe EGR system while putting both scrolls in fluid communication. Inthis case, EGR may be take off both scrolls of the twin scroll turbinevia a common EGR passage upstream of the twin scroll turbine, and theamount of EGR taken of each scroll may be substantially the same.

At 610, method 600 includes adjusting operating parameters in responseto operating the engine with high-pressure EGR and with both scrolls ofthe twin scroll system in fluid communication. Such engine operatingparameters may include ignition timing (spark timing), air/fuel ratio,amount of fuel injected, valve overlap, etc. For example, spark timingmay be advanced and/or an amount of fuel provided to the engine reduced.For example, the engine may be operated with a second amount of positivevalve overlap in at least one cylinder of the engine, where the secondamount of valve overlap is less than the first amount of valve overlapemployed in step 604 described above. As another example, the engine maybe operated with a second amount of spark retard in at least onecylinder of the engine, where the second amount of spark retard is lessthan the first amount of spark retard used in step 604. In someexamples, the engine may be operated with a second amount of fuel, wherethe second amount of fuel is less than the first amount of fuel used instep 604.

In some examples, during certain conditions, e.g., during high speed andhigh load engine operating conditions, valves 124 and 126 may be openedand EGR valve 120 may be closed to put the turbine scrolls in fluidcommunication while shutting off EGR flow to the engine. In this way,turbine performance may be increased, e.g., during high speed and highload conditions, via a reduction in backpressure (e.g., increasedcylinder blowdown volume via branch communication). Additionally, insome example embodiments, an engine may not include an EGR system butmay include a butterfly valve, such as valves 124 and 126, configured tofluidically combine the scrolls of a twin scroll turbine. In this way,turbine performance may be increased during certain engine operatingconditions, e.g., during high speed and high load engine operatingconditions.

FIG. 7 shows an example method 700 for operating a twin scrollturbocharged engine without EGR. At 702, method 700 included determiningif entry conditions are met. As described above, separating the scrollsmay, during some conditions, increase boost response and turboefficiency. For example, conditions for using separated twin scrolls todrive the turbine may include engine operating conditions where theturbine spools up, e.g., engine operating conditions where a speed ofthe turbine increases from a first speed to a second speed, where thesecond speed is greater than the first speed, e.g., during engineacceleration conditions.

Thus, entry conditions may include high load and low speed (RPM) engineoperating conditions, e.g., when a high engine torque is requested by anoperator of the engine, e.g., via an acceleration pedal. For example,the entry conditions may include an engine load greater than a firstpredetermined threshold value and engine speed less a secondpredetermined threshold value. If entry conditions are met at 702,method 700 proceeds to 704.

At 704, method 700 includes operating the engine with both scrolls ofthe twin scroll turbine in fluid communication and without EGR. Forexample, valves 124 and 126 may be opened and EGR valve 120 may beclosed to put the turbine scrolls in fluid communication while shuttingoff EGR flow to the engine.

At 706, method 700 includes adjusting operating parameters in responseto operating the engine without EGR and with both scrolls of the twinscroll system in fluid communication. Such engine operating parametersmay include ignition timing (spark timing), air/fuel ratio, amount offuel injected, valve overlap, etc. For example, spark timing may beadvanced and/or an amount of fuel provided to the engine reduced.

Note that the example systems and methods included herein can be usedwith various engine and/or vehicle system configurations. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various acts,operations, or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedacts or functions may be repeatedly performed depending on theparticular strategy being used. Further, the described acts maygraphically represent code to be encoded as microprocessor instructionsand stored into the computer readable storage medium in the enginecontrol system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, gasoline, diesel and other engine types andfuel types. The subject matter of the present disclosure includes allnovel and nonobvious combinations and subcombinations of the varioussystems and configurations, and other features, functions, and/orproperties disclosed herein.

The following claims particularly point out certain combinations andsubcombinations regarded as novel and nonobvious. These claims may referto “an” element or “a first” element or the equivalent thereof. Suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.Other combinations and subcombinations of the disclosed features,functions, elements, and/or properties may be claimed through amendmentof the present claims or through presentation of new claims in this or arelated application.

Such claims, whether broader, narrower, equal, or different in scope tothe original claims, also are regarded as included within the subjectmatter of the present disclosure.

The invention claimed is:
 1. A method for operating an engine with atwin scroll turbine and an exhaust gas recirculation (EGR) system,comprising: during a first condition, fluidically separating scrolls ofthe twin scroll turbine and operating said engine with reduced EGR froma junction of the scrolls to an engine intake passage; and during asecond condition, fluidically combining the scrolls and operating saidengine with increased EGR from the junction to the intake passage. 2.The method of claim 1 wherein the first condition includes engine loadgreater than a first threshold and engine speed less than a secondthreshold.
 3. The method of claim 1, wherein the second conditionincludes engine load greater than a first threshold and engine speedgreater than a second threshold.
 4. The method of claim 1, whereinduring the first condition the engine is operated with a first amount ofvalve overlap in at least one cylinder of the engine, and during thesecond condition the engine is operated with a second amount of valveoverlap in said at least one cylinder of the engine, where the firstamount of valve overlap is greater than the second amount of valveoverlap.
 5. The method of claim 1, wherein during the first conditionthe engine is operated with a first amount of spark retard in at leastone cylinder of the engine, and during the second condition the engineis operated with a second amount of spark retard in said at least onecylinder of the engine, where the first amount of spark retard isgreater than the second amount of spark retard.
 6. The method of claim1, wherein during the first condition the engine is operated withoutEGR.
 7. The method of claim 1, wherein during the first condition theengine is operated with a first amount of fuel, and during the secondcondition the engine is operated with a second amount of fuel, where thefirst amount of fuel is greater than the second amount of fuel.
 8. Themethod of claim 1, wherein during the second condition EGR is taken offboth scrolls of the twin scroll turbine via a common EGR passage coupledto the junction of the scrolls upstream of the twin scroll turbine, andan amount of EGR taken off each scroll of the twin scroll turbine issubstantially the same.
 9. The method of claim 1, further comprisingduring a third condition, fluidically combining the scrolls of the twinscroll turbine and operating said engine without EGR.
 10. A method foroperating a turbocharged engine including a turbine, comprising: duringa first condition, separating engine exhaust gas pulses to drive theturbine and recirculating a first amount of exhaust gas to an intakepassage of the engine upstream of an intake throttle; and during asecond condition, combining engine exhaust gas pulses to drive theturbine and recirculating a second amount of combined exhaust gas to theintake passage upstream of the intake throttle, where the second amountof exhaust gas is greater than the first amount of exhaust gas.
 11. Themethod of claim 10 wherein the first condition includes high load andlow speed engine operating conditions.
 12. The method of claim 10,wherein the second condition includes high load and high speed engineoperating conditions.
 13. The method of claim 10, further comprisingincreasing valve overlap during the first condition.
 14. The method ofclaim 10, further comprising retarding spark timing during the firstcondition.
 15. The method of claim 10, further comprising advancingspark timing during the second condition.
 16. The method of claim 10,further comprising reducing an amount of fuel provided to the engineduring the second condition.